2 Answers from Attorneys

Sexual relationships between consenting adults are legal. Since it is not a crime, there can be no "charges" as a result. It's also hard to imagine how one partner's family could have a viable civil claim against the other partner, unless the claim is based on more than the relationship.

Adults can do such 'immoral' but legal acts as long as both consent and neither complains to police later. Family members or others could complain to police that 'consent' was not real and that a crime of rape or sexual abuse occurred. A criminal investigation might occur. You'd better hope neither party changed their mind after the fact about 'consent'.